1. Field of the Invention
The present invention relates to the use and charging of rechargeable batteries. More particularly, the invention concerns an unattended battery monitoring system that detects battery conditions such as low charge and impending end-of-battery-life, and responds by taking actions such as sending messages to a remote site and/or shutting down various battery-powered electrical components.
2. Description of the Related Art
Along with increased computing power, portability has been an important hallmark of the electronic age. Some electronic products are manufactured in handheld packages today, where the same component in past years occupied an entire room. Such portability would be meaningless without the availability of similarly portable power supplies, so it is no surprise that batteries have also undergone significant development in storage capability, compactness and other features.
One especially significant development in this area is the rechargeable battery. With rechargeable batteries, an electrically powered device can run for longer without the inconvenient and sometimes expensive task of removing and replacing batteries. In fact, many devices permit battery recharging without removing the batteries. And, if a source of occasional recharging is naturally available, rechargeable batteries can be used to power unattended or remotely located devices, thereby offering even greater convenience and longevity. One such example includes devices that are occasionally recharged with electricity generated by solar or wind energy.
Another example is the cellular untethered TrailerTRACS® product of Qualcomm Inc. The untethered TrailerTRACS product includes a self-contained freight module installed at a freight car such as a semi-tractor trailer. The freight module senses and transmits various status reports regarding trailer position, load, door status, and the like. Each TrailerTRACS module automatically receives recharging power when it is attached to a tractor, and consumes power when it is unattached or “untethered.” Rechargeable batteries provide the TrailerTRACS modules with a greater degree of longevity and self-sufficiency than would be otherwise possible. In some cases, untethered trailers sit dormant for months while their TrailerTRACS modules continue to provide various trailer-related status reports.
Although the TrailerTRACS product yields a number of significant benefits, and even enjoys widespread commercial use today, engineers at Qualcomm Inc. are nonetheless interested in improving the performance and efficiency of the battery monitoring and recharging processes in TrailerTRACS and other unattended products that use rechargeable batteries. Some areas of possible focus concerns improving the ability to monitor and manage battery use, and thereby ensure the availability of sufficient battery power for unattended battery-powered equipment. Monitoring and carefully managing battery use are important because the consequences of poor battery monitoring and management can be severe. For instance, if an unattended TrailerTRACS battery unexpectedly runs out of power, the TrailerTRACS equipment stops transmitting its normal position reports and therefore disappears from remote monitoring equipment, defeating one important benefit normally enjoyed by TrailerTRACS customers. Furthermore, if a battery reaches the end of its life, subsequent recharging cannot prevent the battery from quickly returning to a low charge condition in a relatively fast time, such as one day, thus increasing the possibility of an unexpected, future power loss. Furthermore, technicians must be immediately dispatched to remove and replace the expired battery, despite the resultant inconvenience and labor costs.
As mentioned above, poor battery monitoring and management can result in higher operating costs, inconvenience, and loss of services. Unfortunately, engineers face numerous challenges in trying to develop improved battery monitoring and management techniques. For example, manufacturers' product data sheets often lack accurate information concerning battery charging requirements. In some cases, product data sheets specify battery replacement after a specific number of years of operation. However, depending upon the manner of battery operation, batteries can last notably shorter or longer than expected. If battery life is shorter, the user can suffer an unexpected, premature battery failure. If battery life is longer than expected, the user may replace the battery sooner than necessary, incurring unnecessary replacement costs.
Consequently, known rechargeable battery monitoring and management schemes are not always adequate due to certain unsolved problems.